The present disclosure relates generally to well drilling operations involving magnetic ranging and, more particularly, to calibrating and correcting for noise that may arise during magnetic ranging.
To access certain hydrocarbons in the earth, two or more wells or boreholes may be drilled with a certain spatial relationship with respect to one another. Specifically, one borehole may be drilled such that it has a specific location relative to a previously drilled borehole. For example, heavy oil may be too viscous in its natural state to be produced from a conventional well, and, thus, an arrangement of cooperative wells and well features may be utilized to produce such oil. Indeed, to produce heavy oil, a variety of techniques may be employed, including, for example, Steam Assisted Gravity Drainage (SAGD), Cross Well Steam Assisted Gravity Drainage (X-SAGD), or Toe to Heel Air Injection (THAI). All such techniques may benefit by determining a borehole assembly (BHA) location relative to an existing well.
To drill a new well with a certain spatial relationship with respect to an existing cased well, techniques for magnetic ranging while drilling may be employed. To perform such techniques, a voltage difference may be applied across an insulated gap in a BHA used to drill the new well. In response to the voltage difference, a current may enter the surrounding formation and travel across the casing of the existing cased well, generating a magnetic field that may be measured by a magnetometer in the BHA. Based on the magnetic field measurements, the relative location of the existing cased well to the BHA may be determined. Noise in the measurement of the magnetic field, however, may impede this determination.